Traditional flow-through reactors maximize both the efficacy of the reaction and the heat transferred during reactions by relying on complex tubal configurations. These configurations have historically been intertwined or adjoining, and consequently have suffered poor heat transfer efficiency, considerable heat loss, and reaction inefficiencies. Formidable engineering challenges and high construction costs associated with nesting tubes within one another have presented difficult reactor design barriers and consequently required thick tube walls, long tube runs, large footprints, and extended reaction residence times. This apparatus solves these issues with unique tubular configurations that allow the reactor to be constructed as a monolithic unit, with tube-like channels nestled within each other to maximize heat transfer, efficiency, and reaction speed while minimizing the overall size of the reactor needed for the application.